Question 1

Which of the following statements best describes the role of the transition state in enzyme-catalyzed reactions?

Accepted Answer

Enzymes stabilize the transition state, thereby lowering the activation energy required for the reaction.

Question 2

A researcher is studying an enzyme-catalyzed reaction and observes that increasing substrate concentration does not increase the reaction rate beyond a certain point. Which kinetic parameter is being approached, and what does it represent?

Accepted Answer

The maximal velocity ($$V_{max}$$), representing the rate when the enzyme is saturated with substrate.

Question 3

Which of the following best distinguishes between competitive and noncompetitive inhibition in enzyme kinetics?

Accepted Answer

Competitive inhibitors increase $$K_m$$ without affecting $$V_{max}$$, while noncompetitive inhibitors decrease $$V_{max}$$ without changing $$K_m.$$

Question 4

A Lineweaver-Burk plot of an enzyme-catalyzed reaction in the presence of an inhibitor shows lines with the same $$y-$$intercept but different $$x-$$intercepts. What type of inhibition is this, and what does the $$y-$$intercept represent?

Accepted Answer

Competitive inhibition; $$y-$$intercept represents $$1/V_{max}.$$

Question 5

Which of the following statements about the catalytic triad in serine proteases is correct?

Accepted Answer

The catalytic triad consists of serine, histidine, and aspartate residues that work together to stabilize the transition state and facilitate peptide bond cleavage.

Question 6

Which of the following best describes the difference between the lock-and-key and induced-fit models of enzyme-substrate binding?

Accepted Answer

The lock-and-key model proposes a rigid enzyme active site complementary to the substrate, while the induced-fit model proposes the enzyme changes conformation to fit the substrate.

Question 7

A patient is given a drug that acts as a mechanism-based inhibitor of an enzyme. Which property distinguishes this inhibitor from other types?

Accepted Answer

It forms a covalent bond with the enzyme only after the enzyme attempts to catalyze the inhibitor as if it were a substrate.

Question 8

Which of the following is a correct statement about the Michaelis-Menten equation for a single substrate enzyme-catalyzed reaction?

Accepted Answer

The equation is $$v = \frac{V_{max}[S]}{K_m + [S]}$$, where $$v is $$the initial velocity, $$[S] is $$substrate concentration, $$V_{max} is $$maximal velocity, and $$K_m is $$the Michaelis constant.

Question 9

Which of the following best describes the role of ATP as a cofactor in group transfer reactions?

Accepted Answer

ATP provides a phosphate group that is transferred to substrates, facilitating phosphorylation reactions.

Question 10

Which of the following statements about NAD$$^+/$$NADH and FAD/FADH$$_2 as $$cofactors is correct?

Accepted Answer

Both NAD$$^+$$ and FAD are oxidized forms that accept electrons during redox reactions.

Question 11

Which of the following best describes the difference between aldoses and ketoses?

Accepted Answer

Aldoses contain an aldehyde group at the end of the carbon chain, while ketoses contain a ketone group usually at the second carbon.

Question 12

Which of the following terms describes two monosaccharides that differ only in the configuration around a single chiral carbon atom?

Accepted Answer

Epimers

Question 13

During the cyclization of glucose, which carbon becomes the new chiral center known as the anomeric carbon?

Accepted Answer

Carbon 1

Question 14

Which of the following statements about glycosidic bonds in disaccharides is correct?

Accepted Answer

A glycosidic bond is formed between the anomeric carbon of one monosaccharide and any carbon of another monosaccharide, typically through a condensation reaction.

Question 15

Which of the following best explains why sucrose is a non-reducing sugar?

Accepted Answer

Both anomeric carbons of glucose and fructose are involved in the glycosidic bond, preventing the ring from opening to act as a reducing agent.

Question 16

Which of the following statements about the structure and function of glycogen is correct?

Accepted Answer

Glycogen is a branched polymer of glucose with both alpha-1,4 and alpha-1,6 glycosidic bonds, serving as a storage form of energy in animals.

Question 17

A patient with type O blood can safely receive blood from which of the following donors?

Accepted Answer

Type O

Question 18

Which of the following correctly lists the three components of a nucleotide?

Accepted Answer

Nucleobase, ribose or deoxyribose sugar, and phosphate group

Question 19

Which of the following statements about the directionality of nucleic acids is correct?

Accepted Answer

Nucleotides are linked from the 5' to 3' direction via phosphodiester bonds.

Question 20

Which of the following base pairs is stabilized by three hydrogen bonds in DNA?

Accepted Answer

G-C

BCH 351 Exam 2 Study Guide: Enzymes, Carbohydrates, and Nucleic Acids

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